Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Trillian is a proprietary multiprotocol instant messaging application.

qutIM is free and open-source multiprotocol (ICQ, Jabber, Mail.Ru, IRC, VKontakte) instant messenger.

Psi is a cross-platform powerful XMPP/Jabber client (Qt, C++) designed for the Jabber power users. Psi+ is a development branch of Psi IM XMPP/Jabber client.

FlareGet is a download manager for Windows, Mac and Linux.

Adium is an Open source multi-protocol instant messaging client for Mac OS X, supports MSN, Jabber, Yahoo! and other networks.

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

WeeChat is a free and open-source Internet Relay Chat client, which is designed to be light and fast.

Rambox is a free and Open Source messaging and emailing app that combines common web applications into one.